Program in Neuroscience and Behavioral Disorders, Duke–National University of Singapore Graduate Medical School, Singapore, Singapore

Tin Aung

Singapore Eye Research Institute, Singapore National Eye Center, Singapore, SingaporeDepartment of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore

Purpose :
Chromatic pupillometry has been recently reported as a potential tool for detecting primary open angle glaucoma (POAG), especially at moderate and advanced stages. The aim of our study was to evaluate the capability of this technique to reveal abnormal pupillary responses to light in early-stage POAG.

Methods :
In this cross-sectional study we included 27 early-stage POAG subjects (66.1 ± 7.2 years, 59% males, 93% ethnic-Chinese) and 43 healthy controls (61.4 ± 6.5 years, 23% males, 95% ethnic-Chinese). Empanelled early-stage POAG subjects had a visual field mean deviation (VFMD) of -6dB or better on automated perimetry (Humphrey Field Analyzer, 24-2 SITA-Fast, Carl Zeiss Meditec, Dublin, CA). After an extensive ophthalmic examination, each participant underwent a 2 minute monocular exposure to monochromatic blue light (469 nm) followed by another 2 minute exposure to a monochromatic red light (631 nm) using a modified Ganzfeld dome equipped with an LED lighting system. The light stimuli intensity increased in a continuous logarithmic fashion from 8.5 to 14.5 log photons/cm2.s-1. Direct changes in pupil diameter were measured using an infrared pupilometer and individual dose-response curves were constructed for both stimuli. A two-way repeated analysis of variance (ANOVA) was used to compare pupil constriction profiles between the two groups across different light intensities. All data are reported as mean ± SD.

Results :
Controls and POAG subjects were not different in terms of spherical equivalent (p = 0.9). The average VFMD was -3.3 ± 1.8 dB for POAG subjects and -1.4 ± 1.6 dB for controls (p<0.001). Light-induced percent pupillary constriction from baseline was reduced in early-stage POAG, specifically at moderate to high irradiance levels (above 11 log photons/cm2.s-1) for both blue (p<0.05, Figure 1) and red light (p<0.001). The average maximum pupil constriction was significantly reduced by 14.2% to blue and 9.3% to red light in POAG compared to controls.

Conclusions :
Early-stage POAG is associated with reduced pupillary responses to progressively increasing monochromatic light. This reduction could be the consequence of disrupted integrative functions of the intrinsically photosensitive retinal ganglion cells in early-stage POAG.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.